Cops were questioning a 15-year-old boy last night in a deadly arson fire that raced through a two-story Bronx home, killing two women and injuring six other people, including a toddler.

A firetruck racing to the blaze with its lights flashing and sirens blazing crashed into a minivan, triggering a chain reaction collision that injured 10 people, including two elderly pedestrians.

The blaze broke out at 6:48 a.m. on a stairwell leading to the second floor of the home at 1437 Glover St. in the Parkchester section.

Cops arriving at the scene saw the 15-year-old running away with burns on his hands and face and took him into custody, law-enforcement sources said.

He was being questioned at Jacobi Hospital, where he was being treated for his injuries.

Neighbors awakened by cries of “Fire! Fire!” saw flames shooting 10 feet from the top floor and heard an explosion that shattered the front windows.

“I woke up to screams,” said Nila Reyes, 51, who lives next door. “I looked out and saw flames erupting from the windows of the house. I heard a loud bang and the windows exploded. Stuff came flying out.”

At the urging of the owner, Estella Delacruz, a man and a woman jumped from the second floor. They landed on a first-floor awning, which broke their fall, and they appeared unhurt.

Fire marshals determined that an accelerant – like gasoline – was used to spread the blaze, a Fire Department spokesman said.

The marshals were already investigating an incident at the home on Thanksgiving Day in which an accelerant was poured on the stairs, the spokesman said. The two women, aged 41 and 20, lived on the top floor.

Of the six injured, five suffered smoke inhalation and one a broken leg. A 17-year-old boy and a 2-year-old boy were in critical condition at Jacobi Hospital with smoke inhalation. A total of 110 firefighters battled for 45 minutes to control the blaze.

One of the 25 trucks that responded crashed into a Plymouth minivan at the intersection of Westchester Avenue and White Plains Road. The minivan then crashed into a light pole, struck a 76-year-old couple crossing the street and hit a Ford Taurus.

The Taurus driver, Iven Cameron, 56, of The Bronx, said the elderly man and woman were sent flying onto his windshield. “The van had the green light, but the firetruck had his sirens blazing and the van just didn’t stop,” he said.

The woman was hospitalized with cuts and bruises and the man with a possible fracture.

Two occupants of the van were hospitalized with neck and back pain and six firefighters were treated for bruises and released.